List of help full docker command and its usage with short notes

dockerNotes.md

Writing Dockerfile, docker-compose.yml and its application with nodeJs.

| Dockerfile

Dockerfile is set of some instruction which helps to create custom image which Docker is going to run. To create a Dockerfile, write below 7 mentioned commands in Dockerfile.

1. Docker image of basic dependencies from docker-hub, here node@17 used to setup
   FROM node:17

2. Working/project directory relative (or absolute) path inside container, will be created if it does not exist
   WORKDIR /app

3. Will copy package.json to project directory, it can be "." or /app
   COPY package.json /app

4. Run below command, it will install all dependencies mentioned in package.json

   *Use only one of them as per requirement.

   • RUN npm install --only=production
     • --only=production : used to avoid dev dependencies in production mode
   • Or,

     ARG NODE_ENV   
     RUN if [ "$NODE_ENV" = "development" ]; \    
             then npm install; \   
             else npm install --only=production; \   
             fi
     

     • Also define *ARG NODE_ENV in docker-compose.yml file build block as:

     express-app
     build:
         context: .
         args:
             NODE_ENV: development
     

5. Copy everything from local codebase project directory to container project directory
   COPY . ./

*NOTE: Above mentioned all 5 steps mandotory to create each layer image in a container as final one

6. Set Enviroment variable
   ENV PORT 5000

7. Exposing 5001 for external traffic by docker container to be used
   EXPOSE 5001

8. Command to be run on CMD when container up (with space in a list), could be changed based on environment, its recommended to avoid running npm and only run node and app.js file in production
   CMD ["npm", "run", "dev"]

Useful docker commands

docker build . -> to build image from Dockerfile, where . is location for Dockerfile
docker build -t image-name . -> to build image with image-name
docker image ls -> list all images
docker ps -> list all running container
docker ps -a -> list all stop/running container
docker logs container-name -f -> to see server logs, -f for tail mode
printenv -> print ENV variable in container CLI
docker rm container-name -vf -> to kill docker app container, -v for volumes also, -f for forcefully removal
docker exec -it container-name bash -> login to container CLI with interactive mode with -it argument in bash

Run built image with docker
docker run -p 5000:5000 -d --name container-name container-image-name

• -d : used to detached execution from CLI
• -p : used to specify external:internal port number for traffic handling
• --name : to specify app/container name run with image-name
• --env-file : path to env file, eg. for this ./.env

*Tips: In dev mode, Sync with local code into container in real-time with above command using -v pathToFolderOnLocal:pathToFolderOnContainer flag while running/starting image

$(pwd) can be used for current directory shortcut of local machine, for eg.
docker run -v $(pwd):/app --env-file ./.env -p 5001:5000 -d --name express-app express-app-image

---

| Docker compose

It builds image from Dockerfile and start container in one-go. Only docker-compose command needed as mentioned above, &its little dumb too
To know more about docker-compose.yml variables for diferrent services, look into docker documentation.
docker-compose up -d --build -> to build image and run, --build force to rebuild
docker-compose down -v -> stop docker-compose container and also delete its volumes (don't use -v incase of Database to keep data persistent)
docker inspect container-name -> more detail information about container docker network ls -> List all network of containers docker-compose up -d app_name -> build and start container for specific app_name

Docker Working Notes:

1. after 2nd image building, it cache steps
2. By default it talks to external network. but closed to communicate with internal server
3. 1st kill & restart container to reflect changes except above 1st 5 command values in dockerfile
4. .dockerignore file works like .gitignore
5. Find more details of container like state, NetworkSettings, etc with inspect command.
6. Mention volumes in docker-compose.yml to keep data/file consistent between local and container environment.
7. Different container can talk to each other with thier service_name also (or with ip address), for eg. mongo. It means communication between container can be done with their service_name as ip_address.